The Studies Of Magnetic Properties In Magnetic Multilayer

Recently, magnetic multilayer has attracted considerable attention for fundamental research and technological applications. Here, the overall changes of magnetic properties in surface and interfaces were investigated by a wide variety of theoretical techniques. We also examine the spin reorientation of magnetic thin film. The main content is described as follows:1 Based on the Monte Carlo simulations, magnetizations and spin-wave excitations at the surface,in the bulk for the multilayer with different film thickness, surface interaction are studied. It is found that the Bloch exponent lawM( T) = M(0)(1-BTb) is well satisfied at low temperature (T < 0.5Tc)for total, surface and bulk magnetization (M, Mb, Ms). According to the Bloch exponent law in thequasicrytalline approximation, it is evident that the Bloch constant B changes due to variant coordination number, the structure and surface interaction Js.2 The strong size and surface effect on the critical behavior of different theoretical model is studied. (1) Based on the mean field theory and the Monte Carlo simulations, we examined the magnetic phase of multilayer with different surface interaction to bulk one Js/Jb, and multilayered thickness. It is found that the phase transition temperature depends on the value of Js/Jb and the exchange fluctuations S .The simulated results are consistent with ones derived by mean field theory with transfer matrix method, and well explain the experimental facts. (2) The phase diagrams of a diluted system are analyzed by an effective field theory. In particular, the mean bulk-like transition temperature Tc of the considered system is calculated in general as a function of the differentexchange constants of the system and as a function of the concentration p in the randomly disordered interface layer ApB1-p. The results are compared with the simulated results.3 The spin reorientation of magnetic thin film on a simple cubic lattice is simulated by employing Monte Carlo method. The influence of the magnetic anisotropy and the long-range dipolar interaction on the spin configurations of the system is also studied in detail. Meanwhile, the phasediagrams and the distributions of spin configuration, magnetization, specific heat of the systems are obtained. The results show that in a range of parameters, a transition from out-of-plane to in-plane ordering with the increase of the temperature is possible.